This invention relates to a process for preparing penicillamine or its homologs on the basis of .alpha.-carbon atom branched aliphatic aldehydes, sulfur, ammonia and hydrogen cyanide.
A process of preparing penicillamine is already known in which isobutyraldehyde is reacted with sulfur and ammonia to form 2-isopropyl-5,5-dimethyl-thiazoline-.DELTA..sup.3, which is then converted by reaction with hydrogen cyanide into 2-isopropyl-5,5-dimethyl-thiazolidine-4-carbonitrile, the nitrile hydrolyzed under exclusion of oxygen with hydrochloric acid at a temperature of between 70.degree. and 100.degree. C. to form 2-isopropyl-5,5-dimethyl-thiazolidine-4-carboxylic acid-hydrochloride and this through further hydrolytic decomposition converted into penicillamine-hydrochloride (BEPS 738,520). The disadvantage of this process is that the hydrolysis of the nitrile to the carboxylic acid provides only moderate yields of the acid.